The invention is related to medical and molecular imaging of patients and animals with various scanning machines and methods, and more particularly to sealed calibration and reference sources for such scanning machines.
Scientists and physicians have found that in imaging patients and animals, there are advantages in using combinations of two or more of computed tomography (CT) scanning, magnetic resonance imaging (MRI) scanning, gamma camera scanning, positron emission tomography (PET) scanning, single-photon-emission computed tomography (SPECT) scanning, and optical scanning. Recently, scanners that combine CT and PET functionality have gained favor among physicians. However, since these combination machines are costly, many hospitals, physicians and researchers continue to rely on scanning patients and animals consecutively with a CT scanner and then a PET or SPECT scanner. Since patients often experience great difficulty in remaining motionless not only while being scanned on one machine, but being moved from machine to machine, it can be problematic to register and align the images obtained from the two machines. Furthermore, creating a single “fusion” image from multiple scans requires merging of images with different resolutions and fields of view.
In the context of CT scanning, a “target material” or “target substance” has a mass density greater than about 1 g/cc so as to be visible against a water or water equivalent background but having an upper mass density that is specific to the X-ray energy of the CT scanner so as not to leave artifacts. Artifacts interfere with image quality and it is therefore desirable to eliminate them in images. For example, for a scanner using 50 kVp X-rays, the upper limit of the mass density greater than about 2 g/cc would leave artifacts in the image. For scanners using up to 120 kVp X-rays, the upper limit of the mass density is about 3 to 3.5 g/cc. For MRI scanners, the “target material” or “target substance” is a paramagnetic material. For optical scanners, a “target material” or “target substance” is scintillation material along with a material to activate the scintillation material.
There exist multimodal markers which are formed of target material having wells that are fillable with radioactive solutions for one time use. These markers are inconvenient to use since they require filling with the radioactive solution by the end user immediately before use.
Although the encapsulation portion of known sealed radioactive sources may be formed of materials that show up on a CT scan, these sealed radioactive sources are not designed or intended for use in the calibration, registration or alignment of images taken on different scanners.
It would be valuable to have a source that can be repeatedly used without filling with a radioactive solution prior to use and formed in a variety of shapes and configurations suitable to an end user's requirement.